POLY AZULENES

Poly(azulenes) (structure, Eo. 14.121. and a variety of derivatives, have been synthesized and studied in detail by the Bargon group at IBM [443, 577], who have studied the parent CP as well as the 1-Me-, 1-Phe-, 4,6,8-TriMe-, 4,6,8-TriMe-l-aldehyde, l-(Phe-acetylenenyl)-, and the 1,3,-Di(trimethylsilylacetyleneyl)-derivatives. 

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Poly(azulene) [13] is synthesized by electrochemical polymerization with CIO4 as counterion (similar to that of poly(pyrrole) yielding amorphous polymer films which can be peeled from the anode. Conductivity is 0.01 S/cm. The films may be electrochemically and reversibly discharged to the nonconducting form. 

The simultaneous polymerization and oxidation of azulene with bromine or iodine in acetonitrile have recently been reported. The resultant slightly soluble poly(azulene)-bromine and insoluble poly(azulene)-iodine complexes have lower electrical conductivities than the electrochemically produced polymer, 5x10 and 10 S/cm, respectively. Removal of soluble oligomers from the former leads to a slight improvement of the electrical conductivity. [119,127]. 

During a typical electropolymerization, it is nearly always noted that the net charge transfer is a little in excess of that indicated stoichiometrically, due to the additional oxidation (and doping) that occurs during electrochemical preparation of CPs. For example, while P(Py) and poly(azulene) both stoichiometrically require 2 electrons per monomer for electropolymerization, experimentally a charge of the order of 2.3 electrons per monomer is foimd to be consumed. The excess 0.3 is used to effect a 30% doping of the polymer. 

Fig. 11-32 illustrates the difficulty in studying CPs in the solid state. Here the low-temperature, C MAS spectrum of undoped poly(azulene) is shown together with that of a monomer derivative [441]. The broad resonance for the polymer bespeaks delocalized charge or disordered polymer structure, but does not convey much additional information. 

Write down the structures of the doped and pristine forms of one member of the following classes (discussed in this chapter), and outline one chemical and one electrochemical (if available) synthesis for it P(T) P(T) derivatives P(PP) and related polymers poly(azulenes) ladder polymers poly (quinolines). In which cases are electrochemical (or chemical) polymerizations unavailable, and why ... 

The condensation of a vinylogous formamide with an enamine has been applied to an aza azulene synthesis (351). The point of attachment of the aldehyde to the enamine in condensations with indolenin derived poly-enamines was found to favor the second double bond (352,353). 

These polymers, particularly poly(pyrrole), are most conveniently prepared from the parent molecule via electrolysis. So far, furan, pyrrole, thiophene, and various methylated derivatives have been polymerized by this procedure (10). The anodic polymerization apparently also works for relatively electron rich aromatic compounds such as aniline and azulene (11). 

The improved electrochemical synthesis (7) of poly pyrrole has led to its use as coating for the protection of n-type semiconductors against photocorrosion in photoelectrochemical cells. (8,9) Recently, it was announced that pyrrole was not the only five-membered heterocyclic aromatic ring compound to undergo simultaneous oxidation and polymerization. Thiophene, furan, indole, and azulene all undergo electrochemical polymerization and oxidation to yield oxidized polymers of varying conductivities (5 x 10 3 to 102 cm- ). (10-13) The purpose... 

The photophysical properties of polyacene molecules depend markedly on the number of rings and the fluorescence behaviour of hexacene has now been compared with that of earlier members of the series. A similar comparison has been made of the photophysical properties of catacondensed aromatic poly-cycles. Fluorescence from an upper-excited singlet state has been described for benz[a]azulene derivatives while the fluorescence properties of some antiaromatic molecules have been described in detail. Several thiopyrylium and pyrylium salts have been studied and the effects of various substituents attached to the heterocycle have been examined in terms of the triplet yield. A full evaluation of the photophysical properties of 4-aminonaphthalimide, and its... 

The Ullmann reaction was used in the coupling of a wide variety of aryl halides, Ar-X, where the Ar includes mono-, di-, poly-substituted phenyl [4,5,14], naphthalene [4,5,15,16], azulene [17], pyridine [18], pyrimidine [19], thiophene [4,5,20], carbazole [21], and even ferrocene [22], while X = I, Br, Cl. The reaction was successfully used in the intramolecular cyclization reactions affording four- [23], five- [24], six-membered [25], and some other larger rings [6]. Selected examples where halides 10-13 were converted to biaryls 14-17 are given in the Scheme 2 [14,16,17,19]. 

A number of conjugated heterocyclic polymers, viz., poly(pyrrole) [9], poly(p-phenylene) [10], poly(thiophene) [11], and poly(aniline) [12] are also electrically conducting and continue to be developed and studied for electrochromic devices [13-14 see also the companion chapter in this volume] and ion switching devices [15-16], among others. Polymer films with high electrical conductivity have been generated by electrochemical polymerization of benzenoid, nonbenzenoid and heterocyclic aromatics, in particular from the derivatives of pyrrole, thiophene, carbazole, azulene, pyrene, triphenylene and aniline. The electrochemical approach for making these films is very versatile and it provides a facile way to vary the properties of the films. The realization of the applications for each electroactive polymer depends on the control and particularly the enhancement of the... 

Figure 6. Calibration graphs for glucose obtained with amperometric enzyme electrodes with glucose oxidase covalently bound to different conducting polymers. I. P-amino(polypyrrole). II. poly-(4-aminophenyl)azulen. HI. poly[N-(4-aminophenyl)-2,2 -dithienyl]pyrrole.

Synthesis of Azulenes. Reaction of tropylium cations with allenylsilanes produces substituted azulenes. Typically, commercially available tropylium tetrafluoroborate (2 equiv) is ert5)loyed. The second equivalent dehydrogenates the dihydroazu-lene intermediate to produce the aromatic product. Poly(4-vinyl-P3Tidine) (poly (4-VP)) or methyltrimethoxysilane is used to scavenge the HBF4 produced in the reaction. 

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